1. Field of the Invention
The present invention relates to a device and to a method for providing information about an object location by observing a Doppler frequency response regarding the object location such as may be employed, for example, for determining the positions of game devices, in particular balls.
2. Description of Prior Art
For quite some time, various interest groups have wished to study and understand the sequence of movements of moving objects and/or persons, which requires an exact indication of the object's position both in space and time. What is of particular interest here are, among other things, game balls, in particular in commercialized types of sport, such as footballs, or soccer balls, which are highly accelerated in three-dimensional space, as well as tennis or golf balls. The question of who was the last to touch the object of the game, how it was hit, and in which direction it was accelerated further may be decisive for the outcome of the game, depending on the type of game.
Game devices that are used in high-performance sports, such as tennis balls, golf balls, footballs and the like, nowadays can be accelerated to extremely high speeds, so that a detection of the object during the movement requires highly sophisticated technology. The technical means employed so far—mainly cameras—either completely fail to meet the requirements set forth above, or meet them only to an insufficient degree. Also, hitherto known methods for position finding by means of various transmitter and receiver combinations still leave a large error margin with regard to the spatial resolution of the position indication, with regard to the ease of use of the transmitter/receiver components required, and above all with regard to evaluating the data obtained by means of the transmitter/receiver system, so that it is not yet possible, or at least requires a large amount of effort, to evaluate the results obtained from this data as fast as possible.
It is not only in the field of commercial sports, where movable game devices may be employed, but it is also in the personal field that users have become more and more used to electronic devices indicating various pieces of information to give a user feedback as to how he/she has affected an object, or to provide him/her with information about whether, for example, a game device has crossed a pitch line.
Current statistics methods in commercial applications, such as of the German first football division (Bundesliga), work with recording relatively simple statistics, such as the percentage of ball contacts of a team or the number of corners, free kicks or fouls.
On the other hand, there have been means, for example in tennis, where there is a very plannable, clearly arranged environment with only two players, which measure, for example, the speed of the tennis ball at the serve, such that a viewer is in a position to assess whether a serve was “hard” or “soft”.
What is problematic about such speed measurements which may occur by optical methods is the fact that they do not function within an environment where there is a muddle of players, such as on a football pitch where there are not only two persons being active, but 22 persons, who, in addition, are not positioned in more or less the same place but may form any constellation on the pitch. On the other hand, particularly in football, it is interesting, both for the feedback of the players in training and for the viewers to know, for example, how fast a ball is flying or whether there is a goal situation or an offside situation at hand.
Thus, a multiplicity of tasks, for example locating a ball in a football match, presuppose knowledge of positions of objects. In a football match, for example, one of the most controversial topics is whether or not, in critical situations, the ball has crossed the goal line. For this purpose, it is necessary that the ball's position at the goal line can be measured with an accuracy of about +/−1.5 cm.
There are numerous localization methods based, for example, on optical two-dimensional or three-dimensional sensor having an evaluation system, an exploitation of the known radar principle or of a principle of radio localization.
One principle of radio localization is the localization of objects by electromagnetic wave propagation. For example, a receiver is integrated into an object to be localized or mounted to an object to be localized, the receiver being able to send data to a central transmitting/receiving device upon request. Thereafter, a position of the object is calculated from signal delay times and/or from differences between at least two signals received at different antennas.
Currently available localization methods based on optical 2D or 3D sensors having an evaluation system, or based on the use of conventional radio localization methods, entail high investment and maintenance cost, sensitivity toward environmental conditions and a large outlay in terms of adapting the evaluation algorithms. To achieve fine resolution of a position determination, systems using conventional radio localization are not suitable, since with a small geometrical expansion, differences of various signal delay times are hardly measurable any more. The requirements placed upon system for localizing objects thus are not met, or are met only to an insufficient degree, with regard to economy, robustness, clock time and object independence, for exact position determination, for example, within a range of a few centimeters.